First and fourth authors: Department of Crop Sciences, University of Illinois Urbana 61801; second author: Department of Plant Pathology, University of Nebraska, Lincoln 68583; and third author: U.S. Department of Agriculture-Agricultural Research Service, 1101 W. Peabody, Urbana, IL 61801, and Department of Crop Sciences, University of Illinois, Urbana 61801
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Accepted for publication 14 July 2006.
The soybean cyst nematode, Heterodera glycines, and the fungus that causes sudden death syndrome (SDS) of soybean, Fusarium solani f. sp. glycines, frequently co-infest soybean (Glycine max) fields. The interactions between H. glycines and F. solani f. sp. glycines were investigated in factorial greenhouse experiments with different inoculum levels of both organisms on a soybean cultivar susceptible to both pathogens. Measured responses included root and shoot dry weights, H. glycines reproduction, area under the SDS disease progress curve, and fungal colonization of roots. Both H. glycines and F. solani f. sp. glycines reduced the growth of soybeans. Reproduction of H. glycines was suppressed by high inoculum levels but not by low levels of F. solani f. sp. glycines. The infection of soybean roots by H. glycines did not affect root colonization by the fungus, as determined by real-time polymerase chain reaction. Although both pathogens reduced the growth of soybeans, H. glycines did not increase SDS foliar symptoms, and statistical interactions between the two pathogens were seldom significant.
pathogen population ecology,
quantitative plant pathology.
© 2006 The American Phytopathological Society